1. Field of the Invention
The present invention relates to a liquid carrying method and a liquid carrying apparatus, which use a movable separation film displaceable by the application of the bubble generation pressure generated by the film boiling of liquid. The invention also relates to a liquid discharging method and a liquid discharge head, which use such liquid carrying method and apparatus.
2. Related Background Art
As means for carrying liquid, various ones have been used conventionally.
One of them is a pump that carries liquid using an electric motor. For a pump of the kind, the power supply source is arranged outside the liquid flow path even when the flow of liquid should be produced in a very small quantity by use of a tube whose diameter is several millimeters or less.
Also, there is a method for carrying liquid with the provision of a plurality of heat generating devices arranged on the bottom surface of a liquid flow path where the liquid flows. Here, each of the heat generating devices is driven to generate heat, and create each of the air bubbles by the generated heat. The liquid is then carried by the application of pressure generated by each of the air bubbles thus created.
This method is such that a plurality of heat generating devices, which are arranged on the bottom surface of liquid flow path where liquid flows, are driven one after another to create each of the air bubbles in the direction of the liquid flow, and that the liquid is carried by the application of pressure thus generated by each of the created air bubbles.
Also, there is a method in which at least one heat generating device and a rotator that rotates freely are arranged in the liquid flow path so as to rotate the rotator by means of the pressure of each of the air bubbles created by the application of heat generated by the heat generating device.
For the method of the kind, there is no need for the provision of a plurality of heat generating devices in the liquid flow direction. It should be good enough if only a heat generating device is arranged in a position facing the blades of the rotator. Here, the control is needed just for the sequential rotation if only the center of the rotator is positioned to agree with the center of the heat generating device thus arranged.
For other methods, there have been known a diaphragm type, a gear type, or some others for a quantitative injection pump or the like. Also, there have been known a bellows type or a tube type for carrying liquid in a quantity smaller still, among some others.
Meanwhile, as the methods for discharging liquid, there are disclosed in Japanese Patent Publication No. 61-59916,Japanese Patent Application Laid-Open No. 55-81172, Japanese Patent Application Laid-Open No. 59-26270, and some others, those methods in which bubble generating liquid is caused to generate bubbles by the application of thermal energy through a flexible film that separates the liquid (bubble generating liquid) used for creating each of air bubbles by heat and the liquid (discharge liquid) used for discharging so as to carry over the pressure exerted by generating bubbles to the discharge liquid. In accordance with such disclosed techniques, ink that serves as discharge liquid, and bubble generating liquid are separated by use of a flexible film such as silicone rubber. Then, the structure is arranged so that discharge liquid is not allowed to be in contact with any one of the heat generating devices directly, and at the same time, the pressure exerted by generating bubbles of the bubble generating liquid is carried over to the discharge liquid by the deformation of the flexible film. With the structure thus arranged, it is attained to prevent deposit from being accumulated on each surface of the heat generating devices, while improving the selection freedom of discharge liquids or the like.
However, there is encountered a problem that the structure which uses the flexible film to separate the discharge liquid and the bubble generating liquid completely needs the amount of displacement which is too great to obtain a strong discharge force or to act effectively upon the discharge of a highly viscous liquid, although the structure makes it possible to separate them.
Here, also, there are problems given below as to the conventional liquid carrying techniques described above.
(1) The liquid carrying apparatus that uses an electric motor has its outer diameter of 100 mm to 200 mm even for the smaller ones. Moreover, as described above, the power source should be arranged outside the liquid flow path, and the electric-supply should be made from the outside. Therefore, when this apparatus is incorporated in the smaller and lighter medical equipment, biotechnological equipment, OA equipment, and the like, which are more in demand in recent years, it is inevitable that the intended system is made larger contrary to such requirement of late.
Also, with this apparatus, although a specific quantity of liquid can be supplied continuously, it is impossible to control the supply of liquid in the unit quantity of less than 1/2000 g/sec in particular if a fixed quantity should be carried at certain intervals.
(2) The liquid carrying apparatus, which uses the pressure exerted by each of the air bubbles created by the application of heat generated by heat generating devices arranged on the bottom surface of the liquid flow path, should use the pressure of the created air bubbles that act upon the liquid which also reside on the upstream side of the liquid carrying path. This type of apparatus is not necessarily regarded as the one using efficient method. Also, the liquid which is carried should run on each of the heat generating devices that gives heat to it. Therefore, any liquid whose property is not strong enough against heat cannot be carried easily. There is a fear that burnt substance or other deposit is accumulated on each of the heat generating devices.
(3) The liquid carrying apparatus, which is provided with at least one heat generating device and a rotator that freely rotates, and which is arranged to carry liquid by the rotation of the rotator rotative by the pressure exerted by creation of air bubble using the heat generating device, should provide a wide surface for the rotator in order to receive the pressure exerted by the created air bubble. Therefore, the size of the rotator is a decisive factor that affects the size of the apparatus, hence leading to a problem that the apparatus should be made larger to a certain extent anyway. Also, the liquid which is carried should run on the heat generating device that gives heat to it. As a result, there is a difficulty in carrying the liquid whose property is not strong enough against heat. Also, there is a fear that burnt substance or other deposit is accumulated on the heat generating device.
Now, the present invention is designed in consideration of the problems encountered in the conventional art as described above. It is the main object of the invention to provide a liquid carrying method and a liquid carrying apparatus, which are capable of carrying liquid efficiently by use of a movable separation film displaceable by the application of pressure exerted by each of air bubbles created by film boiling generated in liquid.
It is a second object of the invention to provide a liquid carrying method and a liquid carrying apparatus, which are capable of carrying even the liquid whose property is weaker against heat without causing the accumulation of burnt substance or other deposit on the heat generating devices.
Also, it is a third object of the invention to provide a liquid carrying method and a liquid carrying apparatus, which are made smaller and capable of controlling the supply of liquid in the unit quantity of less than 1/2000 g/sec.
Further, it is a fourth object of the invention to provide a preferable liquid discharge head that uses the liquid carrying apparatus of the present invention.